Testing my ears?

In article <larryhat-0203950903120001 at lhatmaker.uoregon.edu>,
Larry Hatmaker <larryhat at oregon.uoregon.edu> wrote:
[ ... ]
- You'd probably have to find a very specialized tester, though, as most
- of the Aud equipment is calibrated/ designed for the speech frequency
- range (250 to 8000 Hz). Not sure anyone would have Hearing Level
- calibrated outputs for ranges beyond that (HL is calibrated differently
- than Sound Output Levels).
After taking a hearing test a couple of years ago, and being
unimpressed with the detail/testing method, I've wondered how
hearing-test machines are calibrated. Ignoring for the moment the
difference between Hearing Level (perceived?) and Sound Output Level
(energy?), how can you calibrate automatically without having to worry
about calibraing your calibrator (or can you? if not, how do you calibrate
your calibrator?).
(and then, what _is_ the difference between Hearing Level and Sound Output
Level, and how is that calibarted?)
Thanks,
Beorn Johnson
(beorn at eecs.berkeley.edu)